1. Field of the Invention
The present invention relates generally to integrated circuit input/output and, more specifically, the present invention relates to the optical coupling of integrated circuit input/outputs.
2. Background Information
Within the integrated circuit industry there is a continuing effort to increase integrated circuit speed as well as device density. One challenge that integrated circuit designers face with increasing circuit speeds and device densities is the increasingly significant propagation delays of circuit inputs and outputs due to the capacitive loading associated with circuit connections. At slower clock speeds, the capacitive loading on integrated circuit lines is generally not a significant factor. However, as newer integrated circuit design clock speeds continue to climb towards the gigahertz range and beyond, it is evident that one of the major bottlenecks for future integrated circuits, such as for example but not limited to microprocessors, off chip caches, controllers, etc., is the input/output bandwidth and/or round trip delay between and within chips.
Prior art attempts to address the capacitive loading problems associated with increased integrated circuit speeds and device densities have resulted in the use of larger and more powerful integrated circuit input/output drivers on the chip. An undesirable consequence of utilizing larger input/output drivers is that the larger input/output drivers generally consume more power, dissipate more heat and occupy more of valuable area on the integrated circuit die than smaller integrated circuit input/output drivers.
Other prior art attempts to overcome traditional integrated circuit connection limitations have included the use of optical interconnections. Some approaches at optically interconnecting integrated circuits are based on using either gallium arsenide (GaAs) laser diodes and modulating or switching the diodes electrically, or secondly, by using gallium and arsenide-built modulators that amplitude modulate a laser beam passing through an integrated circuit. The modulation used in these prior art approaches is based on electroabsorbtion through strained multi-layer grown molecular beam epitaxy (MBE) films in GaAs integrated circuits. As can be appreciated to those skilled in the art, it is difficult and therefore impractical to integrate or combine III-V based technology, which includes GaAs, with standard silicon based complementary metal oxide semiconductor (CMOS) technology.
Accordingly, what is desired is a method and an apparatus providing high speed optical input/output in an integrated circuit. Such a method and apparatus should enable high speed optical input/output and be compatible with present day CMOS integrated circuit technology. Such a method and apparatus should also enable the use of relatively smaller integrated circuit input/output drivers such that reduced amounts of power are consumed and less integrated circuit die area is occupied.